The recycling machine generally uses a opposite-type photoelectric sensor mounted at a specific location within the banknote identification apparatus, as a trigger mechanism of “starting” and “ending” of data acquisition, counting and banknote testing in a banknote identification system. However, in practice, a paper banknote with a broken hole or a plastic banknote with a transparent window in the transmission path tends to incline excessively or be too close to each other. For a method using signal hopping of a single opposite-type sensor, which is monitored in real time, as a valid trigger, since a hole may lead to a false triggering/leaving event, more than one starting and triggering events may occur for one banknote. For a method that stops after scanning for fixed time duration, two consecutive banknotes being too close to each other may be mistaken as one triggering event. For plastic banknote issued in different countries, the size and position of the window on the plastic banknote vary. Complicated problems as such may bring troubles to normal count determination, data acquisition and flow control in a paper processing apparatus.
Therefore, it is desirable to provide an appropriate triggering/stopping mode to effectively solve the problems that due to a hole of a banknote and inclination of a banknote in conveying, a scanned image of the banknote may not be complete to be identified, and the count of the banknotes may be incorrect.